Pill bugs are usually harmless and are considered by many to be beneficial. They help in the break down of organic matter. Problems may arise when they start munching on seedlings. Protect seedlings with a little diatomaceous earth or a bit of drinking straw split and wrapped around the stems.
Removing plant debris to discourage the sow bugs is all that most gardens will require. Because of the valuable contribution they make to the decomposition process in vegetable matter means that unless they are a direct threat to seedlings or crops, they should be left alone.
You can also effectively trap pill bugs using a half of a cantaloupe that's placed upside down where pill bugs are a problem.

First be sure that the real culprit is the roly ploy, pill bug, sow bug, wood lice, that you see most likley taking advantage of a situation something else created for them. More often than not I find that someone has pretty much wiped out their population of these wee gals and the damage did not stop, because they went after the wrong bug. Simply because you see them there does not mean they did what you see.